MAT E390 Lecture 4: 4 Surface Area and Surface Thermodynamics
2 Aug 2016
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Document Summary
Nature tries to minimize overall energy by reducing surface area exposed. Np"s easily coalesce together to minimize surface energy: Ex: graphene rolls up to become carbon nanotube. Thermal evaporation (a type of physical vapour deposition pvd) Whether one wets another depends on thermodynamics of surfaces. Combination of decreasing the exposed surface area and surface energy to minimize the overall energy. Young"s equation and contact angles: consider a liquid drop on a solid surface (could be a solid on solid) If is big or is small, ( ), system tries to. "conceal" high surface energy of solid surface by covering with liquid. The "complete wetting" is ideal for painting, coating, soldering, and depositing thin films. Wetting can be promoted by: high by cleaning the surface. Removes oxides from the surface (using flux in soldering or acid treatment) 3) low by adding surfactant (add sn to solder to form intermetallic with pieces to be bonded) low by adding (another type of surfactant)
